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JavaScript Express Basics Parameters, Query Strings, and Modularizing Routes Modular Routes

Mitchell Wintrow
Mitchell Wintrow
4,380 Points
Posted by Mitchell Wintrow
Mitchell Wintrow
4,380 Points

Invalid status code. What is that and why doesn't it work?

Hi guys! Thanks for all your help. I'm posting this on here because I read many posts, but unfortunately everything I've tried still hasn't fixed my problem and I don't understand why. I've followed along exactly as Andrew did in the video, but to be honest he gets kind of confusing sometimes by jumping around a lot or changing stuff with the expectation that we should just know what should change back or delete. I keep getting this error:

RangeError [ERR_HTTP_INVALID_STATUS_CODE]: Invalid status code: undefined
    at ServerResponse.writeHead (_http_server.js:259:11)
    at ServerResponse._implicitHeader (_http_server.js:250:8)
    at write_ (_http_outgoing.js:711:9)
    at ServerResponse.end (_http_outgoing.js:825:5)
    at ServerResponse.send (/Users/mitchwintrow/Desktop/Treehouse/Flashcards/node_modules/express/lib/response.js:221:10)
    at done (/Users/mitchwintrow/Desktop/Treehouse/Flashcards/node_modules/express/lib/response.js:1008:10)
    at Object.exports.renderFile (/Users/mitchwintrow/Desktop/Treehouse/Flashcards/node_modules/pug/lib/index.js:448:12)
    at View.exports.__express [as engine] (/Users/mitchwintrow/Desktop/Treehouse/Flashcards/node_modules/pug/lib/index.js:493:11)
    at View.render (/Users/mitchwintrow/Desktop/Treehouse/Flashcards/node_modules/express/lib/view.js:135:8)
    at tryRender (/Users/mitchwintrow/Desktop/Treehouse/Flashcards/node_modules/express/lib/application.js:640:10)

Here is my app.js:

const express = require('express');
const bodyParser = require('body-parser');
const cookieParser = require('cookie-parser');

const app = express();

app.use(bodyParser.urlencoded({extended: false}));
app.use(cookieParser());

app.set('view engine', 'pug');

const mainRoutes = require('./routes');
const cardRoutes = require('./routes/cards');

app.use(mainRoutes);
app.use('/cards', cardRoutes);

app.use((req, res, next) => {
  const err = new Error('Not found!');
  err.status = 404;
  next(err);
});

app.use((err, req, res, next) => {
  res.locals.error = err;
  res.status(err.status);
  res.render('error');
});

app.listen(3000, () => {
  console.log('The application is running on localhost:3000!')
});

Here's my index.js:

const express = require('express');
const router = express.Router();

router.get('/', (req, res) => {
  const name = req.cookies.username;
  if (name) {
    res.render('index', {name});
  } else {
    res.redirect('/hello');
  }
});

router.get('/hello', (req, res) => {
  const name = req.cookies.username;
  if (name) {
    res.redirect('/');
  } else {
    res.render('hello');
  }
});

router.post('/hello', (req, res) => {
  res.cookie('username', req.body.username);
  res.redirect('/');
});

router.post('/goodbye', (req, res) => {
  res.clearCookie('username');
  res.redirect('/hello');
});

module.exports = router;

Here's my cards.js:

const express = require('express');
const router = express.Router();

router.get('/cards', (req, res) => {
  res.render('card', {prompt: "Who is buried in Grant's tomb?"});
});

module.exports = router;

And finally here's my card.pug just to be safe:

extends layout.pug

block content
  section#content
  h2= prompt
  if hint
    p
      i Hint: #{hint}
Mitchell Wintrow
Mitchell Wintrow
4,380 Points
Mitchell Wintrow
Mitchell Wintrow
4,380 Points

Just an update for whoever is responds to my question, I found out how to get past that error but instead discovered another error that prevents me from moving on from the video that follows this video. I had to change the app.use('/cards', cardRoutes); to app.use(cardRoutes);. Now my new problem is this:

When I have my cards.js file set up like this:

const express = require('express');
const router = express.Router();
const {data} = require('../data/flashcardData.json');
const {cards} = data;

router.get('/cards', (req, res) => {
  res.render('card', {
    prompt: cards[0].question,
    hint: cards[0].hint
  });
});

module.exports = router;

it works and I can view the cards page finally. But in the video Andrew said we can just change router.get('/cards', (req, res) => { to router.get('/', (req, res) => { and it will still work. When I change mine to just have '/' it stops working and I get a 404 error so I left it as '/cards' and then it works again. So I followed along in the next video but as soon as I tried doing what he said: '/cards:id' and prompt: cards[req.params.id].question, hint: cards[req.params.id].hint then it stopped working and I got a 404 error again when I typed this into the url: localhost:3000/cards/0.

Can anyone please help me to understand what is going on? Andrews videos are really confusing. I wish Guil was teaching this stuff because I'm really interested in Node and Express and all the server side stuff, and Guil is meticulous and doesn't skip over anything or assume we know something. He just gives it all to us, simple, concise, and meticulous with the details.

1 Answer

jb30
jb30
44,806 Points

In app.js, you have app.use('/cards', cardRoutes);. In cards.js, you have a method starting with router.get('/cards', (req, res) => {. The routes are combined, so you would find the cards page at localhost:3000/cards/cards. If instead you wanted the cards page to be at localhost:3000/cards, you could change either of the '/cards' to '/', but not both.

For the original error, in app.js, you had

app.use((err, req, res, next) => {
  res.locals.error = err;
  res.status(err.status);
  res.render('error');
});

This assumes that err.status has been set to a particular value, such as 404. If err.status has not been set to a value, its value is undefined, which makes res.status(err.status) equivalent to res.status(undefined), which sets the status code to undefined. You could try setting the status code to err.status only if err.status has a truthy value by

if (err.status) {
    res.status(err.status);
}

You could then look at the error page in your browser to see why you had an error.